Process for the treatment of cellulosic fibrous materials



Patented July 19-, 1938 PATENT ()FFlCE PROCESS FOR THE TREATMENT OF CEL- LULOSIC FIBROUS MATERIALS Erwin Mayer, Skoghall, Sweden No Drawing.

Application September 28, 1934,

Serial No. 746,019. In Germany October 3, 1933 -2 Claims.

others, serve to remove or destroy undesirable contaminations, for which reason difierent chemical media are used, and unfavorable action upon the material treated being, however, unavoidable.

The present invention is the result of numerous experiments which, it is surprising,- show that such substances, which enable the formation of an oxidation-reduction system, exert a very favorable action during the improving treatments mentioned if used in very small quantities. Especially thorough experiments prove the application of methylene blue in bucking, mercerizing, bleaching processes and in other processes involving the use of alkaline reacting liquids.

Similar efiects are obtained if, instead of methylene blue, other oxidation-reduction substances, such as phenolindophenol, Nile blue, 3 toluylene blue, Capri blue, new methylene blue are employed.

"If methylene blue is added to a bucking lye and then cotton fabric bucked therewith as usual, decolorization occurs and the cotton fabric shows after the washing a better color and a better strength than cotton fabric which has been bucked in the hitherto known manner without the use of methylene blue. It must be specially remarked that by subsequent bleaching a much better and more lasting white is obtained than when bucking without addition of methylene blue and subsequent similar bleaching method.

If textile materials are bleached without preceding bucking, for instance according to the modern alkaline hydrogen peroxide bleaching or. according to the cold bleaching with sodium .hypochlorite, an addition of methylene blue to the bleaching solution efiects a gradual decolorig zation, and after terminationjof the bleaching and washing the textile materials thus treated .have a much better color, so that a saving in bleaching agents is possible.

However, also the usual bleachings with hypochlorites, for instance chloride of lime, are considerably improved by addition of methylene blue or similarly acting substances, this being of 5 special importance for the celluloseindustry. By

7 the addition of a small quantity of methylene blue to bleaching liquid, a bleached cellulose 55 possessing better properties than without addition of methylene blue is obtained. Just as with textile goods, methylene blue may be added to the alkaline treating liquid for-celluloses which are to be submitted to an alkaline treatment. It is further very remarkable, that also with concentrated lyes a very good effect can be obtained by addition of methylene blue, if cotton or similar textile goods have to be mercerized. Goods results are also obtained if in the treatment of alkali cellulose for the purpose of production of viscose or alkyl cellulose methylene blue is added to the lye. In the preparation of viscose a viscose solution of higher'viscosity can be obtained by addition of methylene blue. If the viscosity is too high for the spinning of the viscose a. suitable product can be obtained by mixing with viscose which has been produced according to the commonly used process.

The process according to the invention can also be combined in a suitable manner with other known methods. Ordinarybucked cotton can for instance be bleached with bleaching agents containing an addition of oxidation-reduction substances, or this addition may take place in the bucking operation preceding the usual bleaching with or without catalysts. The said substances may beadded to the bucking liquid as well as to the bleaching liquid.

The oxidation-reduction agents can be added either in solid form or in the form of solutions,

i. e. aqueous or alkaline, solutions. It must be pointed out especially that the substances can be employed in the form of their colorless leuco compounds with the same good effect. The oxidation-reduction agents or the derivatives of the same, such as salts, lakes may be incorporated either in the material to be treated or in the treating liquids or in both. The oxidation reduction agents may also be brought into the treating liquid in suitable manner, fixed on a separate inorganic or organic carrier, for instance on cotton, and removed again after a certain action period, by which form of addition the present process is not only advantageous as regards ease of application, but also at the same time the problem of the introduction of comparatively small quantities of substances is solved in a simple manner.

The process may be praticed in many ways; some forms in which it may be carried out will be described hereinafter by wayof example:-

1 Cotton, previously untreated, is submitted to a cold bleaching with-sodium hypochlorite (about 2 grams. Cl/litre). Only so much methylene blue is added to the bleaching liquid that it contains about 0.0008 grms. per liter. An eventual subsequent treatment with peroxide can be efiected with or without addition of methylene blue. About 1 to 2% Nazca; and oxygen transmitting catalysts, such as Ni-, Co-, *Ag-sa1ts can be added, besides methyleneblue, to the bleaching liquids which are used.

2. Not easily bleachable fibres are first submitted to bucking, with a bucking lye of usual strength, however, with an addition of new methylene blue, so that the lye contains about 0.0012 grms. new methyleneblue per liter. Ac-

cording to the percentage of contaminations in the fibres, decolorizing will occur sooner or later. If necessary fresh quantities of .new methylene blue may be added. After the bucking, the fibres are'wash'ed and then'bleached without acidifying according to .the commonly used methods with or without addition of methylene blue as in Example 1.

In addition to methylene blue other agents,

such as moistening agents, phenols, alcohols, terpenes, sulfites or other well-known additions may be added to the bucking lye.

The used bucking lye can be used again with or'without the addition of methylene blue, the greatadvantage being obtained according to the invention that the used lye can be used much longer before it has to be regenerated or replaced. The used lyes may be treated with oxidizing agents prior to being used again. It has been found that a lye containing methylene blue produces, when used again and without fresh addition of methylene blue, a much better white than the conmionly used bucking lyes to which no methylene blue in any form has been added.

3. Cellulose of v any origin is bleached according to the known methods for instance with chloride of lime, sodium hypochlorite with-addition of-about 18 grms. methylene blue per 1000 kgsi cellulose. The quantity of methylene blue depends evidently on the percentage of contaminations in the cellulose. The more contaminated the cellulose. is, the sooner the methylene blue will be disclored.

The bleaching of celluloses may, however, be carried out in two or more stages, the whole quantity of methylene blue-being added in the first stage or in aliquot parts in the consecutive stages. In this bleaching in stages, certain pH.- concentrations'can be maintained, 'or there may ing stage with high pH. Reducing and oxidizing bleaching methods may alternate, the methylene blue beingemployed in the one or other or in both methods.

4. Methylene blue is added to the alkaline reacting liquids which are employed for the refining of celluloses. Also in this instance methylene blue is discolored the more rapidly the more hemi-cellulose has been present in the original cellulose; a previously bleached sulfite pulp consumed during the treatment with 8% NaOHf, calculated for dry substance, 21 grms. methylene blue per 1000 kgs. sulfite pulp.

5. Cotton is bleached at 40-100" in a bath'containing 0.5 to 1% hydrogen peroxide with addition of alkaline acting agents, such as ammonia, borax, waterglass and the like and leuco methylene blue.

6. Cotton, linen, artificial silk or other vegetable fibres are saturated with an alkaline solution of methylene blue, for instance a 2% borax solution, and then submitting to bleachingiwith oxidizing agents. If thebleaching is carried through at higher temperature, special attention has to be given to the pH control.

7. Hair or skins are treated during several hours at about 20 'C. with a weak H202 solution containing methylene blue, which reacts almost neutral.

8. 100 .kgs. benzine bone fat istreated with a Nazcos-solu'tion, which contains a small quantity of methylene blue, about 1.5 kgs. of a H202- solution of 30% being added graduallyand the temperature increasedto about 90 C.

The above described process may be used with advantage in the textile, cellulose, artificial silk, fat, wax, soap, glue, leather and similar industries. I

I claim:-'-

1. .The process fortreating .cellulosic fibrous material, said process comprisingsubjecting said material to the action of .an aqueous caustic alkaline solution to which a small proportion of methylene blue has been added. v

2. The process of bucking cellulosic fibrous I material which comprises conducting the bucking operation'witha bucking lye to which a small .proportion of methylene blue has been added. 

